Hip OA Progression Differs By Race

Blacks have more disability; radiographic changes more pronounced in whites

Action Points

The patterns of progression in hip osteoarthritis differed between African Americans and Caucasians, with African Americans having more pronounced disability, while whites had more radiographic progression.

Note that worsening disability along with baseline radiographic features in African Americans suggest an "unmet need" for hip OA management in this population.

After 6 years of follow-up, African Americans tended to have more pronounced disability, while whites had more radiographic progression, according to Amanda E. Nelson, MD, of the University of North Carolina at Chapel Hill, and colleagues.

Worsening disability along with baseline radiographic features in African Americans suggest an "unmet need" for hip OA management in this population, the authors wrote in Arthritis Research & Therapy.

Previous work by the same research team had identified a relatively high frequency of superior joint space narrowing and lateral osteophytes in African Americans. Given that these factors have been associated with increased total hip replacement, the researchers hypothesized that African Americans might have a higher risk of progression compared with Caucasians.

They analyzed data from the community-based Johnston County OA Project, which was designed to represent the civilian, non-institutionalized African-American and Caucasian population, ages 45 and older, living in one of six townships in Johnston County, North Carolina.

Researchers collected baseline data from standardized questionnaires, physical examinations, and paired radiographs from 1991 to 1997, with follow-up data collected from 1999 to 2003. They looked at a number of baseline radiographic features and other factors that predict hip OA progression.

Range of motion progression, which was a reduction in internal rotation of the hip of ≥10 degrees

Total hip replacement progression, or having had a hip replacement at follow-up

Disability progression, or an increase in 0.2 or more in health assessment questionnaire (HAQ) scores

The analysis included 1,422 participants (2844 hips). Patients' average age was 61.4, 40% were male, and 26% were African American. Most participants were overweight or obese (mean body mass index 29 kg/m2), while a third hadn't completed high school, and 8% met criteria for at least mild depression. The mean HAQ score at baseline was 0.3.

African Americans were more likely to be heavier, female, to report less education beyond high school, to be smokers, and to have had longer times to first follow-up. The average time to follow-up for the entire cohort was 6 years.

At baseline, 23% of the participants had definite radiographic hip OA, which ranged from mild to severe.

While the prevalence of definite radiographic hip OA was similar in both racial groups, African Americans were more likely to have a KL grade of 1 and significantly less likely to have a KL grade of 0 compared with Caucasians. Axial joint space narrowing was significantly more common in Caucasians, while superior joint space narrowing was more common in African Americans.

At follow-up, 15% of hips had progressed radiographically, including 16% in Caucasians and 11% in African Americans (P=0.0007). Progression occurred in 15% of hips according to the range of motion definition, in 14% of Caucasians and 19% of African Americans (P=0.0012).

There was no significant difference by race in the number of total hip replacements.

Compared with Caucasians, African Americans were more likely to have a higher frequency of any progression (55% versus 48%), and to have an increase of at least 0.2 points in HAQ scores (40% versus 29%, P<0.0001).

All radiographic features that the researchers investigated, including joint space narrowing, subchondral bone changes, and osteophytes, were associated with at least one of the four hip OA progression definitions.

For example, those with joint space narrowing at any site (axial, medial, or superior) were almost three times as likely to have radiographic hip OA progression, with an adjusted odds ratio of 2.62. They also were 30% more likely to have range of motion progression, with an adjusted OR of 1.31, and were 13 times as likely to have had a total hip replacement, with an adjusted OR of 12.9.

"In the current study, although African Americans were again noted to have a similar prevalence of radiographic hip OA compared with Caucasians, African Americans had less radiographic hip OA progression, but more frequent disability and range of motion progression," the authors wrote.

"Therefore, indications for total hip replacement in this group may be more related to alterations in physical function and disability rather than progressive radiographic change," they observed.

Limitations of the study include a small sample size (less than 1%) for total hip replacement outcomes. In addition, the researchers didn't have continuously measured quantitative joint space width, although they did have semi-quantitative measures of joint space narrowing.

Nelson disclosed support from the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). Co-authors disclosed support from NIAMS, the CDC, the American Geriatrics Society Medical Student Training in Aging Research program, and American College of Rheumatology/Rheumatology Research Foundation Medical Student Research Preceptorship.

Nelson and co-authors disclosed no relevant relationships with industry.

Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner

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